The present invention relates to a method of machining a wafer for making filmed head sliders and a device for machining said wafer, and more precisely relates to a method of lapping or polishing said wafer during a process of forming film layers thereon and a device for lapping or polishing said wafer.
The filmed head slider is made by the steps of: forming a plurality of film layers on a wafer, which is a substrate; and forming various fine patterns in the film layers by etching, etc. In the forming step, a plurality of the film layers are piled on the wafer, so there are formed undulated parts, uneven parts, step-formed parts, etc. on the filmed surface of the wafer. If the film layers are piled with the undulated parts, etc., shapes and measurements of products will be badly influenced.
These days, recording media are made smaller in size but they have large capacity of memory, so the head sliders are required to be highly precisely machined. As described above, if there are undulated parts, etc., formed on the surface of the wafer, measurements of products are badly influenced and yield thereof is also reduced. Thus, the surface of the wafer is lapped or polished so as to remove the undulated parts, etc. and uniformly finish the whole surface thereof.
In the ordinary lapping or polishing step, the wafer is mounted on a machining plate (a lapping plate or a polishing plate), a prescribed pressure is applied to the wafer, and the surface is lapped or polished by the machining plate. However, lapping or polishing is advanced much in the vicinity of an outer edge of the wafer, so lapping or polishing cannot be uniformly executed on the wafer.
A conventional method of uniformly lapping the wafer with a partial load will be explained with reference to FIG. 7. A wafer 12, which is mounted on a machining plate 10, is pressed by a work presser 14. The work presser 14 is properly shifted from a center of the wafer 12, so the partial load is applied to the wafer 12. By using the partial load method, the film layers 16 on the surface of the wafer 12 can be uniformly lapped by the machining plate 10. However, this method cannot always selectively lap uneven parts, and bad wafers are sometimes produced because of excessive lapping by the partial load.
A substrate of the wafer is sometimes bent, and the wafer is sometimes slightly bent while forming the film layers and etching the film layers. In this case, the bend of the wafer must be corrected by force while lapping. However, excessive force sometimes peels off the film layers and deforms end faces of element sections.